SUNNYSIDE — A young man skateboarding while holding onto a truck was was killed Thursday when he lost control and slipped beneath the wheels, police said.

Alexander Ciszewski, 18, of Sunnyside, was hanging onto the right side of a white box truck driving eastbound on 47th Avenue near 32nd Place when he lost his footing and fell just before 11:40 a.m., police said.

"The driver picked up speed," witness Jadon Thompson, 42, said. "That's when the boy went down and lost his balance and fell under the rear tires."

Thompson, who works as an upholsterer at a nearby interior design store, said the driver "ran over him and kept going."

Ciszewski, who was wearing a book bag at the time of the crash, was rushed to Elmhurst Hospital where he was pronounced dead, fire officials said.

Thursday afternoon, family and friends gathered at Ciszewski's Sunnyside home to mourn his loss.

"I just want him to come home and he's not going to come home," said his mother, who declined to give her name.

Friends said he attended LaGuardia Community College, but school could not confirm he was a student.

Police said they were looking for the driver of a 2005 white GMC box truck in connection with the crash. Police were still investigating whether there was any criminality in the crash, NYPD officials said.

Thompson called 911 and tried to help Ciszewski, who was lying facedown in the street with his book bag covering his head. He said he wanted to turn him over, but other bystanders warned him not to move the teen.

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